Session 10: Oral cavity and submandibular region

The Mouth Cavity
The mouth extends from the lips to the pharynx. The
entrance into the pharynx, the oropharyngeal isthmus, is
formed on each side by the palatoglossal fold (Fig. 11.72).
The mouth is divided into the vestibule and the mouth
cavity proper.
Vestibule
The vestibule lies between the lips and the cheeks externally
and the gums and the teeth internally. This slitlike space communicates
with the exterior through the oral fissure between
the lips. When the jaws are closed, it communicates with the
mouth proper behind the third molar tooth on each side.
The vestibule is limited above and below by the reflection of
the mucous membrane from the lips and cheeks to the gums.
The lateral wall of the vestibule is formed by the cheek,
which is made up by the buccinator muscle and is lined with
mucous membrane. The tone of the buccinator muscle and
that of the muscles of the lips keeps the walls of the vestibule
in contact with one another. The duct of the parotid
salivary gland opens on a small papilla into the vestibule
opposite the upper second molar tooth (Fig. 11.72).